1aeb3bd1d4
Reordering meant clicking the up arrow repeatedly - moving a slide from the bottom of a long playlist to the top was a dozen clicks and a page of re-rendering. Rows are now draggable, with a grip so it looks it. Applies to BOTH surfaces: the manager already switches between Lobby Display and Shopfloor Screensaver, so one change covers the lobby TV and the EventSaver playlist. The drop target is shown as a line on the row being dropped against rather than by shuffling rows under the cursor, which reads as the list fighting the drag. The hover preview is dismissed when a drag starts, or it would sit over the list for the whole gesture. Drag and the up/down buttons now share reorderTo(), so both persist through the same call and both recover the same way: a failed save reloads from the server rather than leaving an order on screen that looks saved and is not. dataTransfer.setData is set because Firefox starts no drag at all without it.